ATM permanent virtual circuit and layer 3 auto-configuration for digital subscriber line customer premises equipment

ABSTRACT

The present invention pertains to a method and device for automatically configuring the Permanent Virtual Circuit (PVC) of a Digital Subscriber Line (DSL) Customer Premises Equipment (CPE) and link it to a software interface. The method comprises receiving an ATM cell and checking the ATM cell for an OAM Fault Management (F5) type cell. The OAM type cell allows the PVC to be configured by obtaining a VPI and VCI from the OAM type cell. Otherwise, the CPE configures its new PVC by obtaining a VPI and VCI from a first traffic bearing cell and linking its new PVC to a protocol specific to DSL.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Customer Premises Equipment (CPE)device having its Asynchronous Transfer Mode (ATM) interfaceautomatically configured. More particularly, the present inventionrelates to a method for configuring a Permanent Virtual Circuit (PVC)and layer 3 of a CPE device over an ATM interface.

2. Background Art

ATM is a packet-switching technology that uses fixed-size packets,referred to as cells, to carry the traffic in a network. The ATMstandard allows transmission of intermixed audio, video, and data overhigh-speed links. As well as being used in wide-area networks, the ATMstandard can be used for local-area networks to support multimediaapplications.

The unit of transmission used in the ATM standard is a cell. As shown inFIG. 1, an ATM cell 100 contains 53 bytes of information and has afive-byte header field 102 and a 48-byte payload field 104 carryingdata. Header field 102 contains a Virtual Path Identifier (VPI) 106 anda Virtual Channel Identifier (VCI) 108 which are used for switching cell100 through an ATM network. ATM header field 102 uniquely determinesparameters, associated with a given connection. Within an end userinterface such as a computer, multiple connections can be going on atthe same time.

Within a switch, each ATM cell is switched based on the informationcontained in its header; more specifically based on its VPI and VCI asshown in FIG. 1. A combination of VCI and VPI bits are used to indexlookup tables that contain the switching information.

FIG. 2 illustrates the relationship between a physical transmissioncircuit 200 and a Virtual Path (VP) 202 and a Virtual Channel (VC) 204.Physical circuit 200 supports one or more virtual paths 202. Virtualpath 202 may support one or more virtual channels 204. Thus, multiplevirtual channels can be trunked over a single virtual path 202. ATMswitching and multiplexing operate at either the virtual path or virtualchannel level.

ADSL Customer Premises Equipment is usually configured with onePermanent Virtual Circuit (PVC) over which PPP or bridged request forcomments (RFC) 1483 protocol traffic is supported. The RFC 1483 protocolis dated July 1993 published by Telecom Finland. In a PVC network, suchas ATM, when a circuit is established, the route is chosen from sourceto destination, and all switches (e.g. routers) along the way may takeentries so that they can switch any cells on that virtual circuit. Whena cell comes along, a switch inspects the cell's header to find outwhich virtual circuit it belongs to. Then it looks up that virtualcircuit in its tables to determine which output communication line todirect cell to. Therefore, there is an agreement between a customer anda service provider that the switches will always hold table entries fora particular destination, even if there has been no traffic for months.

FIG. 3 illustrates ATM cell switching using VPI and VCI values. Switch300 maps VPIs and VCIs to different VPIs and VCIs at a connecting point302. The network therefore ties together the VPIs and VCIs used on alink 304 within a physical transmission path 306 to deliver anend-to-end connection to end points 308.

In an end-user network such as the one illustrated in FIG. 4, a CPEdevice 400 communicates with a remote Digital Subscriber Line AccessMultiplexer (DSLAM) 402 through a transmission path 404 having a PVCdefined by a VPI and a VCI. DSLAM 402 communicates with an aggregator418 connected to the Internet 420. CPE device 400 typically comprises ofan ATM interface 406 and a LAN interface 408 connected to a network ofPCs 410 through an ethernet 412. Although CPE device 400 can have ATMinterface 406 dynamically configured with IPCP address negotiation andDHCP client support that belong to layer 3 of a DSL protocol stack asshown in FIG. 5, the ATM PVC still needs to be pre-configured with a VPIand a VCI. A service provider deploying its CPE device actually knowsthe VPI and VCI for the PVC. However, a customer replacing, for example,a bridge with a router, may not know the VPI and VCI of the PVC that heor she is using. A second problem arises when CPE device 400 mustdetermine a type of encapsulation, e.g. PPP over ATM software interface414 or RFC 1483 bridge 416.

A need therefore exists for a method and a device that enable a CPEdevice to automatically configure its PVC and then link it to aninterface such as PPP or RFC bridging so that both layer 2 (ATM PVC) andlayer 3 (DHCP or IPCP) auto-configuration is achieved. Thus, a customerwho buys the CPE device would not need to contact the service providerto find out about the VPI and VPC for the PVC. If the service providersends rfc 1483 bridged traffic or PPP traffic (assuming that CHAP or PAPis not used), the customer would just need to plug the CPE device in andallow it to auto-configure itself.

BRIEF DESCRIPTION OF THE INVENTION

The present invention pertains to a method and device for automaticallyconfiguring the Permanent Virtual Circuit (PVC) of a Digital SubscriberLine (DSL) Customer Premises Equipment (CPE) and link it to a softwareinterface. The method comprises receiving an ATM cell and checking theATM cell for an OAM Fault Management (F5) type cell. The OAM type cellallows the PVC to be configured by obtaining a VPI and VCI from the OAMtype cell. Otherwise, the CPE configures its new PVC by obtaining a VPIand VCI from a first traffic bearing cell and linking its new PVC to aprotocol specific to DSL.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more embodiments of theinvention and, together with the present description, serve to explainthe principles of the invention.

In the drawings:

FIG. 1 is a schematic diagram illustrating the composition of an ATMcell including in detail its header.

FIG. 2 is a schematic diagram illustrating Virtual Circuits and VirtualPaths within a transmission path in an ATM network.

FIG. 3 is a schematic diagram illustrating Virtual Path Identifier andVirtual Channel Identification switching in an ATM node or switch.

FIG. 4 is a block diagram illustrating an end user network in an ATMcircuit.

FIG. 5 is a schematic diagram illustrating the protocol layers in a DSLconnection.

FIG. 6 is a flow chart illustrating a method to automatically configurePVC and layer 3 in accordance with a specific embodiment of the presentinvention.

FIG. 7 is a schematic diagram illustrating an Asynchronous DataTransmission of cells in an ATM circuit.

FIG. 8 is a schematic diagram illustrating an ATM cell containing an OAMfunction.

FIG. 9 is a schematic diagram illustrating a cell transmitted through anaggregate router to support PPP over ATM.

FIG. 10 is a schematic diagram illustrating a composition of a celltransmitted through an aggregate router to support bridged rfc 1483 overATM.

FIG. 11 is a flow chart illustrating a method to automatically configurePVC and layer 3 in accordance with an alternative embodiment of thepresent invention.

FIG. 12 is a flow chart illustrating a method to automatically configurePVC and layer 3 in accordance with an alternative embodiment of thepresent invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

One embodiment of the present invention is described herein in thecontext of an Asynchronous Transfer Mode virtual circuit and layer 3auto-configuration for digital subscriber line customer premisesequipment. Those of ordinary skill in the art will realize that thefollowing description of the present invention is illustrative only andnot in any way limiting. Other embodiments of the invention will readilysuggest themselves to such skilled persons having the benefit of thisdisclosure. Reference will now be made in detail to an implementation ofthe present invention as illustrated in the accompanying drawings. Thesame reference numbers will be used throughout the drawings and thefollowing description to refer to the same or like parts.

In the interest of clarity, not all the routine features of theimplementations described herein as described. It will of course beappreciated that in the development of any such actual implementation,numerous implementation-specific decisions must be made to achieve thedevelopers specific goals, such as compliance with system and businessrelated constraints, and that these goals will vary from oneimplementation to another. Moreover, it will be appreciated that suchdevelopment effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking of engineering for those ofordinary skill in the art having the benefit of this disclosure.

In accordance with a presently preferred embodiment of the presentinvention, the components, process steps, and/or data structures areimplemented using an electrical circuit in a Digital Subscriber Linecustomer premises equipment. This implementation is not intended to belimiting in any way. Different implementations may be used and mayinclude other types of electrical circuits, computing platforms, programstorage devices and/or computer programs. In addition, those of ordinaryskill in the art will readily recognize that devices of a less generalpurpose nature, such as hardwired devices, devices relying on FPGA(field programmable gate array) or ASIC (application specific integratedcircuit) technology, or the like, may also be used without departingfrom the scope and spirit of the inventive concepts disclosed herewith.

FIG. 4 is a block diagram illustrating an end user network in an ATMcircuit.

FIG. 5 is a schematic diagram illustrating the protocol layers in a DSLconnection.

FIG. 6 is a flow chart illustrating a method to automatically configurea Permanent Virtual Circuit of a Digital Subscriber Line CPE and layer3.

Referring now to FIGS. 4, 5, and 6, a CPE device 400 that automaticallyconfigures its PVC would perform the following steps.

At step 600, CPE 400 receives a cell from a DSLAM 402 through a physicaltransmission path 404. At step 602, CPE 400 examines the received cell.If the received cell is determined to be an Operations and Maintenance(OAM) cell, step 604 is performed. OAM cells are special purpose cellswhose function provide a set of diagnostic and alarm reportingmechanisms such as fault management. As illustrated in FIG. 7, an OAMcell 700 includes a VPI 702, a VCI 704, an OAM field 706 and otherfields 708. CPE 400 therefore can identify whether it received OAM cell700 by looking at the received cell content for OAM field 706. At step604, CPE 400 may grab VPI 702 and VCI 704 from OAM cell 700 andtherefore create a PVC since both VPI and VCI are known. Once the PVC iscreated, CPE 400 replies to OAM cell 700 according to its functionwhether it is fault management or performance management at step 606.Otherwise, if the received cell is not an OAM cell, step 608 isperformed.

At step 608, CPE 400 determines whether the received cell is a firstcell of a packet by measuring the elapse time between the received celland a previous cell on the same PVC. FIG. 8 illustrates the flow ofcells in an asynchronous transmission. Although idle cells 800 separatetraffic bearing cells 802 and 804, idle cells 800 are discardedautomatically by physical layer of CPE 400. The elapse time betweentraffic bearing cells 802 and 806 is usually less than 50 ms whereas theelapsed time between the first cell of a BPDU (PPP) packet and the lastcall of the previous BPDU (PPP) packet is more than 800 ms. At step 610,once CPE 400 determines that the elapse time between traffic bearingcells is less than 800 ms, CPE 400 discards the received cell through abuffer. Otherwise, if the received cell is first traffic bearing cell802 following idle cells 800, step 612 is performed.

At step 612, CPE 400 can then grab the VPI and VCI from the receivedcell because traffic bearing cells contain VPI and VCI in their headeras previously illustrated in FIG. 1.

When a Service Provider configures an aggregate router, such asaggregator 418, to support protocols such as PPP or bridged RFC 1483over ATM, CPE 400 receives many messages from the aggregate router. Inthe case of PPP over ATM protocol, CPE 400 receives regular Link ControlProtocol (LCP) configuration requests messages. In the case of bridgedRFC 1483, CPE 400 receives regular (Bridge Protocol Data Unit) BPDUspanning tree messages. Instead of discarding the received ATM cellscontaining these messages because no PVC is configured, CPE 400 caninstead look inside these cells and try to determine whether theycontain a valid LCP header or a BPDU header.

At step 614, CPE 400 determines whether the received cell contains anLCP header as shown in FIG. 9. In a cell 900 containing an LCP header, apayload 902 has its protocol values set to LCP. LCP Cell 900 alsocontains other fields 908. When a cell containing an LCP header isreceived, step 616 is performed. At step 616, CPE 400 looks at thereceived LCP cell 900 to obtain VPI 904 and VCI 906 enablingconfiguration of a new PVC only if VPI 904 and VCI 906 of PPP PVC arethe same as VPI 702 and VCI 704 of OAM cell 700. Once the new PVC isconfigured, CPE 400 links the new PVC to PPP interface module 414, asshown in FIG. 4, so as to bring up the PPP interface to start layer 3auto-configuration. Otherwise, if the received cell does not contain aLCP, CPE 400 performs step 618.

At step 618, CPE 400 determines whether the received cell contains aBPDU header as shown in FIG. 10. In a cell 1000 containing a BPDUheader, a payload 1002 has its protocol values set to BPDU. BPDU cell1000 also contains other fields 1008. When a cell containing a BPDUheader is received, step 620 is performed. At step 620, CPE 400 looks atthe received BPDU cell 1000 to obtain VPI 1004 and VCI 1006 enablingconfiguration of a new PVC only if VPI 1004 and VCI 1006 of BPDU PVC arethe same as VPI 702 and VCI 704 of OAM cell 700. Once the new PVC isconfigured, CPE 400 links the new PVC to RFC interface module 416, asshown in FIG. 4, so as to bring up the RFC 1483 bridged interface tostart layer 3 auto-configuration. Otherwise, if the received cell doesnot contain BPDU, the received cell is discarded at step 622.

Another implementation of the present invention may be in the form of aprogram storage device readable by a machine, embodying a program ofinstructions, executable by the machine to perform a method forauto-configuring a Permanent Virtual Circuit (PVC) of a customerpremises equipment device over an Asynchronous Transfer Mode (ATM)network.

While embodiments and applications of this invention have been shown anddescribed, it would be apparent to those skilled in the art having thebenefit of this disclosure that many more modifications than mentionedabove are possible without departing from the inventive concepts herein.

For example, FIG. 11 illustrates an alternative embodiment of thepresent invention. OAM cells are not identified by CPE device 400 sincethey are likely not to be received by CPE device 400. FIG. 12illustrates another alternative embodiment of the present invention. Atstep 1212, after determining the VPI and VCI, CPE device 400 may createthe new PVC in the same step 1212 instead of waiting until step 1216 orstep 1220 when the new PVC is linked to PPP interface or RFC 1483interface.

In addition, the present invention is not limited to protocol such asPPP or RFC 1483 but may be applied to any other protocol specific to DSLthat sends periodically cells that are differentiable.

The invention, therefore, is not to be restricted except in the spiritof the appended claims.

1. A method for a auto-configuring a Permanent Virtual Circuit (PVC) ofa customer premises equipment device over an Asynchronous Transfer Mode(ATM) network, said method comprising: receiving a plurality of ATMcells from a digital subscriber line access multiplexer; checking saidplurality of ATM cells for an Operation and Maintenance (OAM) cell, saidOAM cell allowing the PVC to be auto-configured by obtaining a VirtualPath Identifier (VPI) and a Virtual Circuit Identifier (VCI) from saidOAM cell; configuring the PVC by obtaining said VPI and said VCI from afirst ATM cell; and linking the PVC to a protocol, said protocol beingapplicable to DS1. 2-20. (canceled)